The field of the invention pertains to arrows for archery and, in particular, to improvements to speed, accuracy, and delivered power of an archery arrow.
The standard archery arrow is a suitable length shaft with vanes or fletching affixed at the posterior end. When propelled by a bow, the arrow""s flight is stabilized by virtue of the fletching""s drag against air resistance. While this construction does achieve a relatively straight line of flight (except for the effect of gravity on the flight), it does so at the cost of energy loss in direct proportion to distance of flight as the air resistance is a substantially constant function of arrow flight speed.
If rotation can be imparted to the arrow, the arrow will be stabilized in a manner similar to a bullet shot from a rifled barrel firearm. Some attempts have been made to provide rotation to an arrow. U.S. Pat. No. 5,971,875 discloses a slot which drives against circumferentially arranged dimples. However, this device makes no provision for a disengagement mechanism that will allow for rotation of the arrow while the arrow is engaged in the bow string prior to release. A frequent result is the failure of the arrow at the nock and bow string interface. As shown in this patent, a form of external fletching is required to achieve rotation of the arrow upon release from the bow string.
By eliminating the fletching, there will be an increase in arrow speed and delivered energy. The increase in arrow speed will result in a straighter trajectory and enhanced accuracy.
The new arrow spin device comprises a screw shaft which is cylindrical at the leading and trailing ends thereof and inserted in the posterior end of the arrow shaft. A rotary spin is imparted to an arrow shaft about its longitudinal axis at initial bow string release by engagement of the screw shaft with a guide integral with the arrow shaft.
As the screw shaft becomes fully inserted into the arrow shaft in response to the bow strings""s force, the arrow shaft becomes free to rotate about anterior and posterior cylindrical surfaces on the screw shaft. Upon release from the bow string, the arrow shaft is rotating and the arrow will travel faster and with less deviation by virtue of the ballistic spin imparted. This spin allows the arrow to avoid the need for external fletching.